Project 1: Producing smoothly coordinated movements during performance of complex behaviors is an essential goal of the nervous system. To accomplish this, sensory information must be integrated continuously in order to construct a representation of objects in the world. This critical function requires the ability to distinguish between self-generated and object motion, to integrate diverse sensory information, and to plan and execute simultaneous motor behaviors. The interactions among neural structures that mediate selection and execution of coordinated movements, and the mechanisms that resolve the inherent conflict between stabilizing reflexes and motor commands are critical issues in understanding the neural control of coordinated action. The neural control of coordinated eye-head movements is an experimental system that has provided significant insights into the neural mechanisms mediating visual orienting behaviors. Directing the line of sight (gaze) towards interesting objects enhances our perception of the object and provides a way to construct and maintain an internal model of the world. These changes in gaze direction are generally accomplished by coordinating the eyes and head, and provide an excellent model system for studying the neural control of orienting behaviors, the coordination of multiple body segments, spatial orientation and transformation of sensory information into motor commands. The goals of the proposed research are to elucidate the neural computations and mechanisms required for coordination within the context of visual orienting movements. The cerebellum has long been implicated in the refinement of motor commands and correction of errors between commanded and executed movements. The brainstem control of eye-head coordination during visual orienting behaviors has been and continues to be a major focus of research in this lab. The experiments proposed here extend this work in order to investigate the role of the cerebellum in modifying and/or correcting the motor commands generated by brainstem regions. The proposed research will test the differential roles of the caudal and rostral portions of the fastigial nucleus in coordinating movements of the eyes and head. Experiments will also test the hypothesis that gaze shift commands generated by activity in the superior colliculus are refined by activity in the caudal fastigial nucleus (cFN). The primary goals of the research in the lab are to understand the neural mechanisms mediating coordinated actions. Disruption of these mechanisms can result from stroke or disease and often have devastating consequences such as spatial disorientation, saccadic dysmetria and/or ataxia. The proposed research will facilitate early detection of disturbances and lead to new treatments of these disorders.